1. Field of the Invention
The invention relates to the field of data presentation and computer graphics. More specifically the invention relates to the stacking or arrangement of symbols on top of one another, creating a multi-dimensional visual impression in a geographic information system (GIS) environment. As a result, the invention provides the location and magnitude indications of data in a geographic information system (GIS) environment.
2. Description of the Related Art
In the present geographic information system environment, it is common practice to use different size of symbols to represent intensity or frequency of occurrence. For example, on a map of the United States, to indicate the location of major cities, one usually draws a dot on the map where each city is located. To indicate the population size of each city, one approach is to vary the size of the dot. That is, cities with higher populations will be represented by bigger dots. The advantage of this approach is that a viewer has direct impression of the relative size as well as the location of major cities. The disadvantage is that the dot size of some cities (such as New York) are so big compared to the others (such as Washington D.C.) that they may block other details (such as roads, states lines) on the map. Another approach is to use different colors (or symbols) to indicate different population sizes. The advantages is that it will not block other details on the map, because all cities have the same size of symbols. The disadvantage is that a viewer has to look at the legend to find out what color or what symbol representing what population sizes. Therefore this approach does not give the viewer a direct impression of the size and location. A variation of this approach is to use darker colors to represent higher populations. The is fine if there are only a few categories. If there are many categories, it will be difficult to distinguish which colors are darker. Another approach is to use a vertical or horizontal bar. The bar can be placed on the map where the city is located, to indicate location. The height or width of the bar is proportional to the city's population size, to indicate magnitude. By looking at the location and height (for vertical bar) or width (horizontal bar) of the bar, one can get an both location and magnitude impression. In this approach, although one can choose any color or size of the bar, however, one is limited to the single shape and form (that is, limited to the shape and form of a bar only).
The current invention is to provide another approach to both location and magnitude representations. To indicate the locations of major cities, as mentioned in the above example, each city will be represented by a symbol on the map. To indicate different population size of each city, repeated symbols will be stacked on top of each other. The higher the stack of symbols, the higher the population. One can choose any style, color or size of symbols. One can stack or arrange the symbols according to any mathematical functions.